Hi Steve,
Trimble Connect Sync doesn't check Tekla licenses to upload / download the files. It is quite surprising that you were able to see missing model elements while the file itself had been synced.
Are you checking the models in Trimble Connect Browser app or Windows app after the upload - where you are seeing the missing elements ? Can you please send a screenshare video to our Support team (connect-support@trimble.com) , so that we can investigate.
Regards
Darshan Kamat